Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $231.56   13.468%   $262.7465   $262.75   $262.75   $262.70  
  Purchase #2 $215.75   10.198%   $237.7522   $237.75   $237.75   $237.80  
  Purchase #3 $188.28   11.578%   $210.0791   $210.08   $210.10   $210.10  
  Purchase #4 $35.95   7.470%   $38.6355   $38.64   $38.65   $38.60  
  Purchase #5 $212.43   8.214%   $229.879   $229.88   $229.90   $229.90  
  Purchase #6 $66.81   6.576%   $71.2034   $71.20   $71.20   $71.20  
  Purchase #7 $54.71   7.136%   $58.6141   $58.61   $58.60   $58.60  
  7 purchase totals = $1,005.49       $1,108.9098   $1,108.91   $1,108.95   $1,108.90